The Siemens 5SM3446-6 is a 4-pole residual current circuit breaker (RCCB) from the SENTRON 5SM3 series, rated 63 A at 400 V AC, 50 Hz.
At 4 width units (72 mm wide, 90 mm tall, 77 mm deep), it occupies four 18 mm slots in the enclosure — plan the rail layout accordingly. The supply can enter from top or bottom, which simplifies busbar routing in a crowded panel. Installation depth is 70 mm, leaving 7 mm behind the DIN rail for wiring clearance.
Thermal derating and ambient limits
Above that, derate linearly: 59.22 A at 50 °C, 55.44 A at 55 °C, 51.66 A at 60 °C, 47.88 A at 65 °C, and 44.1 A at 70 °C. Storage range is -40 to +75 °C, which is wider than the operating range; that limit governs handling and shelf life, not running conditions.